Recently, material used for a semiconductor device has extended from inorganic material to organic material, and the characteristics of a semiconductor device or a fabrication process can be further optimized by using the special characteristics of the organic material, which are not present in the inorganic material.
One such organic material is polyimide. Polyimide has high adhesion and low leakage current. Thus, a polyimide film obtained by forming polyimide on a surface of a substrate may be used as an insulating layer, and may also be used as an insulating layer in a semiconductor device.
As a method for forming such a polyimide film, there is known a film forming method based on deposition polymerization using, for example, pyromellitic dianhydride (hereinafter, abbreviated as “PMDA”) and 4,4′-diaminodiphenylether including, for example, 4,4′-oxydianiline (hereinafter, abbreviated as “ODA”) as raw material monomers. The deposition polymerization is a method for thermally polymerizing PMDA and ODA used as raw material monomers on a surface of a substrate. In the related art, there is disclosed a film forming method for forming a polyimide film by evaporating the monomers of PDMA and ODA with a carburetor, supplying the evaporated vapor of each of the PDMA and ODA to a deposition polymerization chamber, and deposition-polymerizing the same on the substrate.
In order to form a polyimide film having excellent film quality by using deposition polymerization at a low cost and within a short time, it is required to continuously supply a fixed amount of vaporized PMDA (hereinafter, referred to as “PMDA gas”) and the vaporized ODA (hereinafter, referred to as “ODA gas”) to the substrate. Thus, a film forming apparatus for forming a polyimide film preferably includes a supply mechanism for supplying raw material gases composed of the PMDA gas and the ODA gas into a film forming container and an exhaust mechanism for exhausting gases from the film forming container to decompress the interior of the film forming container.
However, a film forming apparatus for forming a polyimide film by supplying the PMDA gas and the ODA gas to the substrate has the following problems.
In order to form a polyimide film on the surface of the substrate by supplying the raw material gases composed of the PMDA gas and the ODA gas, the supply amount of the raw material gases within the plane of the substrate is preferably uniform, and to this end, the flow of the raw material gases on the surface of the substrate is preferably a laminar flow. However, the flow of the raw material gases on the surface of the substrate that is generated as the raw material gases are supplied into the film forming container by the supply mechanism and as the gases are exhausted from the interior of the film forming container by the exhaust mechanism is not a laminar flow, degrading the uniformity of the supply amount of the raw material gases within the plane of the substrate. In addition, besides a film thickness of the formed film, the uniformity of film quality is also degraded.